I'm a former rower, though not the one you were DMing previously. Long story short, you don't want to row at a high resistance, especially when you're getting started. Very easy to throw your back out already, and the higher resistance only makes that more likely.

I favor the air based machines over the water ones as they're much easier to move around, stand upright out of the way, and literally can't leak.

More important than anything though, please please please watch a rowing technique video (or ten). It's mostly leg and core that move the boat, not arms.

I'll shoot you a DM, should you have other questions too :)

don't tell me to run I HATE running

REAL
me too friend

Now, i'm no expert on rowing machines, but i would say the 200 dollar rowing machine i got on Amazon for Christmas 2 years ago was an amazing investment in my own fitness. At least it was when i used it almost every day last year, until i stopped in llike January, but I'm getting back into it

You have the same build as me so i wouldn't worry about being too out of shape to use it, you just might have to start at a lower resistance. Idk anything about levels of resistance but the one i got goes from 1-16 and 16 is really hard. i do like 2.5 miles at max resistance and it's a workout i tell you hwut

It isn't really hard on your knees but idk i can't guarantee it's good for your gf because i've never had her knee issues. But i got one because running was killing my calf and knees

It's definitely more than just cardio btw rowing like 30 minutes, 4-5 miles a day for most of a year my body literally changed shape like my shoulders blew the fuck up

Consider buying one on amazon that allows for free returns and returning it if you don't like it (make sure it has free returns though lol)

Rowing machines are good for all round fitness, but correct technique is non-intuitive and takes a long time to learn. Done correctly it will build core strength, legs and shoulders. But most importantly cardiovascular fitness. It is low impact so it should be fine on your knees as long as you aren't splaying your legs apart on the drive. I would personally recommend an exercise bike / spin bike in place of a cheap rowing machine for cardio especially if you can't be bothered with the technical aspects. Just sit on the bike, watch tv, get your heart rate above 130bpm for an hour, easy peasy.

I love me a rowing machine but it is fairly easy to hit top limits. Maybe buy a used one for cheaper and sell it again if it doesn't work out for you?

Depending on how high your ceilings are I would consider a speed rope instead. This plus some calisthenics and maybe a pullup bar is all you need.

8ft is probably enough, 10 is for sure. Rowing is great but it takes up a lot of space, is expensive and takes a lot of time. You can do a whole rope workout in 20 minutes and nothing builds work capacity like the rope imo. It's also pretty low impact. You feel like a jackass at first, tripping over the rope every three hops, but it only takes a couple of sessions to get used to the cadence.

Rowing is not bad on the knees, tends to be harder on the back in my experience but I also don't have knee issues. Top resistance on the machine isn't that big a deal imo people tend to set their resistance way too high on average. Every time I go to the gym the resistance on the rowers is maxed when 5-6 is the sweet spot. If it's not enough people should be pulling harder instead of jamming the lever to 10.

If you do go the rower route I would look for one that has a chain instead of a cable.